The use of polymeric materials such as ethylene-based compositions in an extrusion blown film process is well-known. The extrusion blown film process employs an extruder which heats, melts, and conveys the molten polymeric material and forces it through an annular die. The ethylene-based film is drawn from the die and formed into a tubular shape and eventually passed through a pair of draw or nip rollers. Internal compressed air is then introduced from the mandrel causing the tube to increase in diameter forming a bubble of the desired size. Thus, the blown film is stretched in two directions, namely in the axial direction, i.e. by the use of forced air which expands the diameter of the bubble, and in the lengthwise direction of the bubble, i.e. by the action of a winding element which pulls the bubble through the machinery. External air is also introduced around the bubble circumference to cool the melt as it exits the die. The film width is varied by introducing more or less internal air into the bubble thus increasing or decreasing the bubble size. The film thickness is controlled primarily by increasing or decreasing the speed of the draw roll or nip roll to control the draw-down rate.
The bubble is then collapsed into two doubled layers of film immediately after passing through the draw or nip roll. The cooled film can then be processed further by cutting or sealing to produce a variety of consumer products.
Despite the research efforts in producing the polymeric materials suitable for blown films, there is still a need for a polyethylene blend composition suitable for blown film, providing improved output rates. Furthermore, there is still a need for a method of producing a polyethylene blend composition suitable for blown film, providing improved output rates.